2-morpholinosulfinylbenzothiazoles



United States Patent O 3,532,693 2MORPHOLINOSULFINYLBENZOTHIAZOLES Alfred Bay Sullivan and Robert Henry Campbell, St. Albans, W. Va., assignors to Monsanto Company, St.

Louis, Mo., a corporation of Delaware No Drawing. Filed June 1, 1967, Ser. No. 642,712 Int. Cl. C07d 87/46 US. Cl. 260247.1 3 Claims ABSTRACT OF THE DISCLOSURE The disclosure is new compounds such as 2-morpholino-sulfinylbenzothiazole of the formula The compounds are prepared by the action on the corresponding 2-morpholinothiobenzothiazole of an aqueous solution of an alkali metal hypohalite. The new compounds are useful accelerators for the vulcanization of rubber.

CROSSREFERENCE TO' RELATED APPLICATION The co-pending application of Alan Ieifrey Neale and Terence James Rawlings, Ser. No. 642,671, filed June 1, 1967, now U.S. Pat. 3,454,590 discloses a process for preparing 2morpholinosulfinylbenzothiazole by the reaction of benzothiazole 2-sulfinyl chloride with morpholine.

BACKGROUND OF THE INVENTION SUMMARY OF THE INVENTION This invention relates to new compounds that are useful vulcanization accelerators for rubber and to a process for their synthesis. The compounds are 2-morpholinosulfinylbenzothiazoles of the formula \C R- p N where X is morpholine or a mono-, di-, tri-, lor tetraalkylmorpholine, The R and R are identical or dissimilar combinations of hydrogen, N CONH OH, halogen,

alkyl, or alkoxy. The alkyl groups contain 1 to carbon atoms. The compounds are prepared in a solvent by the action on the corresponding 2morpholinothiobenzothiazole of an aqueous solution of an alkali metal hypohalite.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific examples of the compounds of the invention are:

3,532,693 Patented Oct. 6, 1970 The compound 2-morpholinosulfinylbenzothiazole is prepared according to the following equation:

Five grams (0.02 mole) of Z-morpholinothiobenzothiazole and ml. of methanol are charged into a 200 ml. three-necked flask fitted with a stirrer, a reflux condenser and a dropping funnel. The mixture is warmed to 50- 60 C. Forty grams (0.07 mole) of sodium hypochlorite, in which the excess NaOH has been neutralized by adding sufiicient 3 molar hydrochloric acid dropwise to obtain a final pH just above 7, is added to the mixture from the dropping funnel over a 30-minute period. The mixture is stirred vigorously during this period and the temperature is maintained at 5060 C. The resulting product is isolated by precipitation with 500 ml. of cold water. The white precipitate is filtered, washed and dried. The yield is about 40%. The 2-morpho1inosulfinylbenzothiazole has a melting point of 9193 C. Gas chromatographic analysis, infrared, and ultraviolet analyses of the product are consistent with the structure Z-morpholinosulfinylbenzothiazole.

Gas chromotography: (Column-3% SE-SZ on 60/80 mesh Gas Chrom-Z; temperature200 C.) The product elutes immediately following the starting material as expected due to its higher molecular weight, thus lower volatility.

Infrared spectroscopy: The infrared spectrum of the isolated product is very similar to that of the starting material with the exception of a strong band at 930 cm. which can be assigned to the S O stretching vibration.

Ultraviolet spectroscopy: The product has a maximum absorbance at 278 mp. with a specific absorptivity of 40.7 l./g.-cm. in methanol. Upon reduction with NaBH, in methanol the characteristic ultraviolet spectrum of 2- mercaptobenzothiazole is obtained (A =320 In/1.).

The remaining compounds of this invention are prepared in a similar manner to the 2-morpholinosulfinylbenzothiazole preparations with comparable results. The compound 2-(2,6-dimethyl-4 morpholinosulfinyl)benzothiazole has a melting point of 108 1l0 C.

Sodium hypochlorite is the preferred alkali metal hypohalite useful as an oxidizing agent in this invention. The solvent for the process is a Water-miscible solvent in which the reactants are soluble and the solvent is not readily oxidized by the oxidizing agent. The preferred solvent is methanol.

The new compounds can be used as accelerators in the vulcanization of natural and synthetic sulfur-vulcanizable rubbers. Synthetic rubbers that can be vulcanized include polymers of 1,3-butadienes, for example of 1,3-butadiene .4 I torque, R.M.T., is recorded as a measure of thernodulus of the sample.

TABLE Mooney Scorch at 121 C. Rheorneter at 144 0.

17 1335-155 R.M.T. t2 tun kz 2-Morpholinosulfinylbenzothiazole 48.3 12.1 47.7 11.0 38.8 .099 2-Morpholinothiobeuzothizaole 43.8 4.7 54.5 11.8 30.5 .148 2-(2,6-(limethyl4-m0rpholinosulfinyl))-benzothiazole 50.4 13.0 46.4 11.4 40.8 .094 2-(2,(i-dimethyl-4-morpl10lin0thio)-benzothiazole 43. 4 6. 6 126 rubber by conventional means, for example using an internal mixer or a roll mill, or by adding a solution or suspension to a rubber latex, giving a mixture which is subsequently vulcanized at an elevated temperature. This temperature is one that is appropriate to the particular rubber concerned, for example a temperature in the range of ll55 C. where the composition is based on natural rubber, or a temperature in the range of l40-160 C. where the composition is based on styrene-butadiene rubher.

The amount of accelerator used depends on a number of factors including for example the type of rubber and the use for which the vulcanized product is required. The amount is, however, usually within the range of 0.3 to 5 parts by Weight, and more especially within the range of 0.3 to 2 parts by weight, per 100 parts by weight of rubber, for example 0.5 and 1.5 parts by weight.

The data in the table, infra, illustrate the use of the compounds of this invention as accelerators for the vulcanization of rubber. The data includes results for the corresponding sulfenamide. A masterbatch composition is prepared by compounding the following:

N 1,3 dimethylbutyl N phenyl p phenylenediamine (an antidegradant) Accelerator In one test reported in the table, a sample of rubber is placed in a Mooney plastometer. The time, t taken for the reading of the instrument to reach 5 units above the minimum viscosity of the sample is recorded as a measure of the scorch time. The higher this figure, the greater the scorch delay action of the accelerator.

In the second test method, cure time and modular properties of a rubber sample are measured using the Monsanto Oscillating Disk Rheometer described by Decker, Wise, and Guerry in Rubber World, December 1962, page 68. The scorch time, t is recorded as the time to reach 2 units above the minimum viscosity of the sample. The cure time, 1 is recorded as the time in minutes to reach 90% of the maximum cure, and the maximum The data in the table illustrate the greater degree of delayed action of the compounds of this invention as accelerators in comparison with the corresponding sulfenamide. The figures for the cure rates and moduli of vulcanizates represent high degrees of accelerator activity. Comparable results are obtained with the accelerators of this invention not illustrated.

It is intended to cover all changes and modifications of the examples of the invention herein chosen for purposes of disclosure which do not constitute departures from the spirit and scope of the invention.

We claim:

1. A compound of the formula alkyl, or alkoxy and the alkyl groups contain 1 to 5 carbon atoms. 2. A compound according to claim 1 of the formula and named 2-morpholinosulfinylbenzothiazole.

3. A compound according to claim 1 of the formula S OH:

and named 2 (2,6 dimethyl 4 morpholinosulfinyl) benzothiazole.

References Cited UNITED STATES PATENTS 2/1952 Mingasson 260306.6 7/1960 Stansbury et al 260551 ALEX MAZEL, Primary Examiner J. H. TURNIPSEED, Assistant Examiner US. Cl. X.R. 260-5, 79.5, 786 

